Photographic processing methods are normally continuous. Accordingly, the photographic processing baths, for example development baths, bleaching baths, fixing baths, stop baths, stabilizing baths or bleaching/fixing baths, have to be constantly regenerated in accordance with the quantity of photographic material to be processed to ensure that the concentration of processing chemicals is kept at the required level. Since, in most photographic processing steps, chemicals are released from the material into the processing bath and can cause problems through accumulation, the regenerating solution is added in a quantity which is larger than that which the material transports from the bath in any event, so that an overflow is formed. Both for economical and for ecological reasons, this overflow is collected, cleaned, chemically worked up and returned to the system.
To minimize losses of chemicals, it is standard practice to free the photographic material from adhering liquid before it leaves the chemical tank. Different methods are used for this purpose, including for example rubber lips ("wipers") lying on one or both sides of the material, vacuum extraction or blowing off with compressed air. With optimal settings and geometric adaptation, all three processes have an efficiency of at most 50 to 70%. In none of the processes mentioned are the chemicals which do not adhere to the surface of the material, but are present in the emulsion layers, removed or prevented from being carried over. Accordingly, there are significant losses of chemicals which are only removed from the material in the following washing stages and enter the wastewater.
The problem addressed by the present invention was quantitatively to prevent such losses and hence to enable photographic processing baths to be almost completely recycled.
It is known from DE-A-4 011 613 that the chemicals carried over from the chemical baths can be collected by subsequent washing in a multiple-compartment system and that the liquid accumulating in certain compartments can be concentrated by reverse osmosis or concentration by evaporation and subsequently returned to the circuit. This process is complicated in terms of procedure and equipment and lacks efficiency because the waters laden with chemicals always flow out from the middle compartment of three or five compartments.